title: Muscle acylcarnitines during short-term fasting in lean healthy men.
abstract: The transition from the fed to the fasted resting state is characterized by, among other things, changes in lipid metabolism and peripheral insulin resistance. Acylcarnitines have been suggested to play a role in insulin resistance, as well as other long-chain fatty acid metabolites. Plasma levels of long-chain acylcarnitines increase during fasting, but this is unknown for muscle long-chain acylcarnitines. In the present study we investigated whether muscle long-chain acylcarnitines increase during fasting and we investigated their relationship with glucose/fat oxidation and insulin sensitivity in lean healthy humans. After 14 h and 62 h of fasting, glucose fluxes, substrate oxidation, and plasma and muscle acylcarnitines were measured before and during a hyperinsulinaemic-euglycaemic clamp. Hyperinsulinaemia decreased long-chain muscle acylcarnitines after 14 h of fasting, but not after 62 h of fasting. In both the basal state and during the clamp, glucose oxidation was lower and fatty acid oxidation was higher after 62 h compared with 14 h of fasting. Absolute changes in glucose and fatty acid oxidation in the basal compared with hyperinsulinaemic state were not different. Muscle long-chain acylcarnitines did not correlate with glucose oxidation, fatty acid oxidation or insulin-mediated peripheral glucose uptake. After 62 h of fasting, the suppression of muscle long-chain acylcarnitines by insulin was attenuated compared with 14 h of fasting. Muscle long-chain acylcarnitines do not unconditionally reflect fatty acid oxidation. The higher fatty acid oxidation during hyperinsulinaemia after 62 h compared with 14 h of fasting, although the absolute decrease in fatty acid oxidation was not different, suggests a different set point.
authors.affiliation: Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam 1105 AZ, The Netherlands. m.r.soeters@amc.uva.nl
authors.forename: Maarten R
authors.initials: MR
authors.lastname: Soeters
authors.forename: Hans P
authors.initials: HP
authors.lastname: Sauerwein
authors.forename: Marinus
authors.initials: M
authors.lastname: Duran
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Wanders
authors.forename: Mariëtte T
authors.initials: MT
authors.lastname: Ackermans
authors.forename: Eric
authors.initials: E
authors.lastname: Fliers
authors.forename: Sander M
authors.initials: SM
authors.lastname: Houten
authors.forename: Mireille J
authors.initials: MJ
authors.lastname: Serlie
mesh_terms: D000328:Adult; D000886:Anthropometry / Q000379:methods; D001786:Blood Glucose / Q000378:metabolism; D002153:Calorimetry, Indirect / Q000379:methods; D002331:Carnitine / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism; D005215:Fasting / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology; D050356:Lipid Metabolism / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology; D055815:Young Adult
chemical_list: D001786:Blood Glucose; C116917:acylcarnitine; D002331:Carnitine